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We have designed an antimatter thruster capable of reaching the nearest star.  A plan for antimatter fuel production is now needed.
We have designed an antimatter thruster capable of reaching the nearest star.  A plan for antimatter fuel production is now needed.
We have designed an antimatter thruster capable of reaching the nearest star. A plan for antimatter fuel production is now needed.
62 backers pledged $2,280 to help bring this project to life.

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Antimatter Fuel Production

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In 2002 we were funded by the NASA Institute for Advanced Concepts to perform preliminary work on an antimatter-based propulsion system. This campaign seeks to fund a continuation of our mission to develop an antimatter thruster capable of reaching (or exceeding) 5% of the speed of light. The goal is to enable interstellar travel with the initial requirements of accelerating, decelerating, and studying a nearby solar system all within a human lifetime.

For a more complete presentation and a detailed look at our past work, go to http://www.antimatterdrive.org and view our ever-growing body of content.

When a person in the general public first finds out about the serious development of antimatter propulsion, their initial reaction is often "Can we make antimatter?" Our standard response is that humanity has already been able to produce 2 nanograms per year at the Fermi National Accelerator Laboratory ("Fermilab"). In fact, one of our lead scientists worked at Fermilab for 14 years on antimatter production, storage, and usage. In fact, that scientist led, along with Bill Foster (now U.S. Congressman IL-11) [http://www.billfoster.com/], the approval, design and construction of the antiproton Recycler ring pictured below.

Particle accelerator tunnel containing a proton accelerator (lower ring called the Main Injector) and an antiproton storage ring (upper ring called the Recycler).
Particle accelerator tunnel containing a proton accelerator (lower ring called the Main Injector) and an antiproton storage ring (upper ring called the Recycler).

 Can Enough Antimatter be Made?

When funded by NASA we estimated that it would require tens of grams of antimatter to enable an interplanetary mission. But as stated above, past antimatter production was limited to 2 nanograms per year. At this rate it would require approximately 2 million years to produce enough antimatter for a single mission. Clearly, if this was the best that humanity could do, we would not have launched this Kickstarter campaign.

Antimatter can be any combination of antiprotons, antineutrons, and positrons (antielectrons). Fermilab produced antiprotons. In order to produce a propulsion system fuel, positron (anti-electron) production would also be required. Given that it is much easier to create positrons than antiprotons, for the purposes of this campaign we will concentrate solely on making antiprotons.  

At Fermilab the process of producing antiprotons started with accelerating a large quantity of protons to 120 Gev (an energy comparable to roughly 120 times the mass of the proton using the famous equation E=mc^2). The majority of this acceleration occurred in the Main Injector pictured above. This acceleration was repeated every 1.7 seconds, day and night, week after week. Once at 120 GeV the protons were extracted and sent into a metal target (pictured below).
Fermilab antiproton production target.
Fermilab antiproton production target.

By rotating the assembly the radiation damage could be spread out. By translating the assembly perpendicular to the beam direction, the depth of material seen by the protons and antiprotons could be varied in order to optimize antiproton production.

Antiprotons sometimes form for when a proton disintegrates upon collision with a target nucleus. The resultant particle shower sometimes includes an antiproton. For every million protons on target, Fermilab was able to capture 15 antiprotons. The thicker the target, the more protons can be converted into antiprotons. But as the target depth is increased, the newly created antiprotons are increasingly annihilated before exiting the target and scattered into a very diffuse cloud. In order to capture as many antiprotons as possible, a lithium lens was placed immediately behind the target to focus that cloud. One of the Fermilab lenses is pictured below.

Fermilab lithium lens used to focus antiprotons formed in a thick target.
Fermilab lithium lens used to focus antiprotons formed in a thick target.

After travelling through the lithium lens the antiprotons were directed into a pair of particle accelerators called the Debuncher and the Accumulator. The purpose of the Debuncher was to reduce the large energy spread of the antiprotons. The purpose of the Accumulator was to "stack" antiprotons into a tight beam. An important technology employed was stochastic cooling, the invention of which earned the Nobel Prize for accelerator physicist Simon van der Meer in 1984. These accelerators are shown in the picture below.

Fermilab accelerator operations specialist inspecting components in the antiproton Accumulator storage ring.  The Debuncher accelerator is behind him on the inside wall of the tunnel.
Fermilab accelerator operations specialist inspecting components in the antiproton Accumulator storage ring. The Debuncher accelerator is behind him on the inside wall of the tunnel.

This state-of-the-art antiproton production infrastructure was designed to produce antiproton beams used in the Tevatron proton-antiproton collider in order to perform high-energy particle physics experiments, such as the discovery of the Top quark. For the purpose of fueling an interstellar mission, an optimized antiproton production infrastructure will be quite different.

First, instead of a thick target, a very thin target will be used. While this geometry will produce fewer antiprotons per accelerated proton, the antiprotons that come off the target will form a much tighter beam. The anticipated yield of antiprotons per proton is expected to be close to 1%. By utilizing multiple targets the same number of proton interactions can be generated. Therefore, the increase in antiproton intensity is expected to be near a factor of 1000.

Second, the number of protons can be increased. A relatively modest proton intensity increase factor of 5 is assumed.

Third, instead of the use of synchrotrons such as the Main Injector, linear acceleration for the same proton beam current yields an increase antiproton production factor of 200,000. Applying all of these improvement factors, the antiproton production rate can be increased from 2 nanagrams per year to 2 grams/year. An antiproton production rate of 2 grams/year is sufficient to fuel an interstellar mission every decade or so. During the course of the research supported by this campaign further upgrades will be invoked to decrease the mission fueling time toward the goal of less than 4 years.

How Much Would it Cost?

The second question is usually "How much would it cost to fuel such a propulsion system?". There are two answers to this question. First, there is the cost of the equipment needed to produce antimatter. Second, there is the ongoing cost of operating the antimatter production facility year after year.

In order to address the issue of equipment cost, it is instructive to look at an historical example. That example is civilian nuclear power. If one does not include the cost of security and fuel rod storage, civilian nuclear power plants are quite economical and by far the cleanest power generation technology from an ecological point of view. Chicago is powered by several nuclear power plants which provide the area base load at a fraction of the cost of even coal-powered plants.

None of these power plants would have been possible without the Manhattan project and all of the associated nuclear fuel efforts at sites such as Oak Ridge National Laboratory. In today's dollars the cost of producing the fissile material was approximately $24 billion. The fissile material in the fuel rods that power today's civilian plants was largely produced during that time. Of course, this material was primarily used to produce atomic bombs, fusion bombs, nuclear powered ships, and research reactors.

Another example is the United States manned space program from 1961 through 1969, at an estimated cost of $23 billion in 1960's dollars, or approximately $140 billion in today's dollars. The incremental cost of Apollo 17 was only a couple of billion dollars because of the investments made getting to the moon the first time.

Similarly, the equipment cost for producing grams of antimatter will be born not only by interstellar missions, but also by other applications such as advanced radiation therapies and scanners for homeland security. These other applications have been the subject of prior research and patents.  The point is that strategic capabilities, such as helium harvesting, manned space flight, and fissile material production, have been national priorities from time to time.
Prior to the work anticipated to take place during this campaign we are not prepared to hazard a guess of the cost of antimatter production equipment. First, we must design a facility and research the specific technologies best suited to accomplish the initial goal of producing 2 grams of antimatter per year.  The cost of operating such a facility can then be estimated.
Because large numbers of protons must be accelerated to approximately 120 GeV, the electrical bill assuming a reasonable conversion efficiency of 45% would be the dominant cost. Using Fermilab as a starting point, the proton beam power is on the order of 350 kW. Assuming 90% energy recovery from the proton beam by decelerating the spent proton beam, at 2 grams/year the estimated electrical power consumption would be 40 GW. The United States nuclear power capability is 100 GW, and the total electrical power capacity of the United States is 411 GW.
Because the production of antimatter can be synchronized with the availability of solar power, a solar cell array approximately 30 km by 30 km could power the entire facility. While again there would be the issue of equipment cost in the solar cells, tracking systems, and power conversion infrastructure, once built such a facility could be quite economical.
The point of this discussion is not to prove that it is either desirable nor practical to engage in large scale antimatter production, but rather that it is within the scope of humanity's capabilities. For now, we can only conclude that it NOT impossible!  At the completion of this campaign, we should have a much better understanding of these costs.

Choice of Antimatter Fuel

The initial choice of antimatter fuel during our NASA funding was antihydrogen (one antiproton surrounded by a single positron).  Since this study concentrated on objects in the far reaches of our solar system including the Oort Cloud and Kuiper Belt (see graphic below), the duration of antimatter fuel storage was not too serious of a concern.  For example, the travel time to the inner edge of the Oort cloud could be as small as a few years.

Local destinations near our solar system.
Local destinations near our solar system.

But at 5% of the speed of light, it would take 90 years to reach the nearest confirmed planet Proxima b.  We have concluded that travelling through a solar system at this velocity would preclude any measurements that would yield useful information.  Therefore, the spacecraft would need to decelerate and go into orbit around either the star or Proxima b itself.  To decelerate from this velocity, antimatter would need to be transported across the interstellar void.

The storage of antihydrogen for this period of time would be quite problematic.  Like its normal matter cousin, antihydrogen has a high vapor pressure even at cryogenic temperatures.  This means that antihydrogen molecules would continuously boil off the surface of the solid antihydrogen snowflakes that were originally envisioned.  We need a fuel with a much lower vapor pressure.

So the answer comes down to producing nuclei containing antineutrons.  After considerable study of the literature, the proposed first step in the process of nucleosynthesis is the reaction in which two 70 MeV antiprotons are collided to produce an antideuteron (an antiproton bonded to an antineutron) plus a negative pi-meson.  In actuality the two antiprotons would not be at the same energy so as to produce the antideuteron with a kinetic energy high enough to be efficiently captured by a third storage ring.

As seen in the sketch below, half of these stored antideuterons are then collided with antiprotons to form antihelium-3 (one antiproton plus two antineutrons).  The other half of the antideuterons are collided with half of the antihelium-3 nuclei to from antihelium-4 (two antiprotons bonded to two antineutrons).  This reaction also produces an antiproton that is trapped and used over again.  The last stage is to collide the antihelium-3 and the antihelium-4 nuclei to from antiberyllium-7.

A proposed plan for the nucleosynthesis of antilithium.
A proposed plan for the nucleosynthesis of antilithium.

There are a couple of points to note in this nucleosynthesis plan.  First, all of these reactions are well measured with their normal matter cousins.  Second, collision energies and partners were chosen so that theoretically no antimatter is lost in the entire process.  The loss is restricted to mass-less gamma-rays and low-mass pi-mesons.

Once the antiberyllium-7 is produced it is decelerated and stored in an electromagentic trap.  By itself, the antiberyllium-7 nuclei are stable.  But the next step is the introduction of positrons to form atomic antiberyllium-7.  By cooling the antiberyllium-7 nuclei into a crystal lattice wherein their mutual repulsion creates coupling between the nuclei, this positron capture will be enhanced.

Once converted into atomic antiberyllium-7, positron capture decay will occur with a 53.22 day half-life.  Eventually all of the antiberyllium-7 decays into antilithium-7, which is stable.

The long-term storage and manipulation of grams of antillithium will be addressed in a future campaign.  The current campaign will concentrate on designing the specific particle accelerator hardware and detailing the production rates at each step of the above process.  Cost estimates of the equipment and operations will be generated.  Basically, we will produce a design report that can be used to build an antilithium factory.  This design report will also be used as the basis for future experiments (funded by future campaigns) wherein this entire nucleosynthesis plan will be tested using normal matter (to keep expenses down).

Use of Funds

The amount of money requested in this campaign is far below that required to fully cover expenses.  Like a company producing a new product, sometimes it is necessary to sell the product below cost in order to build a customer base.  Still, the requested funds will be used to partially reimburse employees and to defer the cost of some software needed to complete the proposed work.

If more funding becomes available, it means that our universe of backers has increased.  Based on this demonstration of interest a follow-on campaign will be proposed that is matched in scope to this interest.

Summary

We plan to reignite our previous development effort on antimatter-based propulsion (see http://www.antimatterdrive.org).  We will do this through a series of small campaigns, each focused on a particular issue.  For this campaign the goal is to develop the process and design the equipment necessary to produce the antimatter fuel for such a mission. The specific campaign goals are:

  • Design the particle accelerator complex needed to produce several grams of antiprotons each year.
  • Estimate the equipment and operational costs of such a complex.
  • Produce a design report that specifies all of the processes and equipment necessary for the production of antilithium, the proposed antimatter fuel of choice for interstellar missions requiring deceleration once at the destination solar system.
  • Estimate the equipment and operational costs for antilithium production.
  • Plan a program of future campaigns aimed at experimentally demonstrating the nucleosynthesis and storage of antilithium (using normal matter to keep costs low).

Risks and challenges

The goals of this campaign are purposely restricted to tasks that do not require permission or cooperation from external entities such as NASA or Fermi National Accelerator Laboratory. Instead, we will concentrate on designs and reports aimed at bolstering future campaigns, giving us the necessary time to reestablish such relationships.

Because we are new to crowdfunding, we have promised only one reward that requires shipping and handling. All other deliverables will be electronic in nature, allowing us to concentrate our efforts on the science. If there is a significant demand for items such as T-shirts, mugs, or other tangible items, we will consider expanding our rewards categories appropriately in the future.

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    FINAL REPORT

    To show our gratitude, your name will be added to our website "hall of supporters". Within a month of the end of the project you will receive via email a PDF final report containing calculations, drawings, artist conceptions, and conclusions.

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    DIGITAL ARTIST RENDERING

    Within a month of the end of the project a graphic of the antimatter fuel production scheme will be delivered in PDF format via email.

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    For the duration of the project you will receive monthly full-color PDF project newsletters including news, updates, pictures, and educational articles about antimatter physics.

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    FERMILAB TOUR

    Enjoy a personalized behind-the-scene tour of the Fermi National Accelerator Laboratory next time you happen to be in the western suburbs of Chicago. Bring your family and friends (limit of 12 people per tour, limit of 1 tour per pledge).

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Funding period

- (14 days)